EpiPen Needle

Submitted by:
Greg Friese, MS, NREMT-P, WEMT
President, Emergency Preparedness Systems LLC
Lead Instructor, Wilderness Medical Associates

    Is it long enough to reach lateral thigh muscle?

A common student question during the allergies and anaphylaxis lecture is “how long is an EpiPen needle? (EpiPen Jr. 1/2″ and EpiPen 5/8″).”

I just read the summary of a study that used ultrasound to measure the distance between the skin and lateral thigh muscle in a convenience sample of 248 children ages 1 to 12 years old. The researcher concluded that the depending on the child’s weight the needle would not reach the muscle in 12% of the children that weighed less than 30kg and 30% of children that weighed greater than 30kg.

For the wilderness medicine providers these findings are mostly merely interesting. If you administer epinephrine to treat anaphylaxis and the patient’s symptoms don’t improve it could be for many reasons including slower absorption of the epi by the subcutaneous route instead of the intramuscular route. Remember the WildMed Anaphylaxis protocol includes administration of epinephrine, diphenahydramine, and prednisone, as well as PROP and evacuation. If the patient’s anaphylaxis symptoms persist or return (biphasic reaction) follow the protocol for administration of additional epinephrine. Finally, if time and symptoms allow it may also be prudent to make sure to press the auto-injector against the patient’s bare skin instead of injected through a single layer of clothing.

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